How long does a dog stay in heat? Well it ultimately depends on what exactly you mean by heat and at what point your dog is in the cycle to start with. From the age of six months or older, most dogs will start going into heat and they will do so for the rest of their lives. Dogs do not go through menopause like people do because their heat cycles are not like periods experienced by women. Whether you are planning on breeding your dog or you need to know for how many day you must keep her separated from male dogs, learning more about the duration of a dog's heat is important.
The Proestrus Stage
Dog's don't go into heat at the flip of a light switch. Before going into official heat, they go through a "pre-heat" stage which is known as proestrus.
During this stage, the female dog's body is getting ready for reproduction. Estrogen levels will gradually rise while progesterone levels should remain relatively low.
As this happens, the female dog's body will undergo several physical changes. Her vulva will start swelling and look puffy and there will be a bloody discharge. The discharge may not be noticed much as the female dog licks herself clean often, therefore these first signs of impending heat may be missed.
Some dogs may undergo slight behavior changes such as getting more irritable and some may even lose their appetite.
During this pre-heat stage, male dogs may start becoming interested in the female, but the female will not allow any of them to mount. As the days progress though, she may try to escape from confinement in search of a mate. Generally, this stage will last between 7 and 10 days, with the average length being nine days.
The Estrus Stage
Experienced breeders call this stage "standing heat" because it is during this stage that female dogs will stand for the male, allowing him to mount. During this stage, estrogen levels remain quite the same , while progesterone levels begin to rise, What are the signs a dog is in the estrus stage? One of the most evident signs is the bloody discharge turning from bloody to light pink or straw colored. The female dog may flirt and play with the male dog, even mounting the male at times, and then finally "flagging her tail" moving it to the side so the male can mount. During this stage, she may urine mark more often on walks and in the yard to signal her availability. This urine is rich in pheromones which draw male dogs to her whereabouts. Don't be surprised to find several stray dogs by your door! Generally this stage last also about six to 10 days, with the average length being nine days.
The Diestrus Stage
As dogs don't go into heat at the flip of a light switch, they don't go out it abruptly either. The diestrus stage is the time when female dog will no longer be interested in males, but male dogs may still stick around for some time. Her vulva will shrink back to normal size and the straw-like discharge will no longer be present. What happens from this point forward depends on whether she is pregnant or not. If she is pregnant, the diestrus stage will last up until the birth of the puppies, so about 60 days as diestrus is calculated as the time between the last day the female dog accepts a male up until the end of pregnancy. If she is not pregnant, the diestrus phase will not be any different from the anaestrus stage (see below).
The Anaestrus Stage
The root word "ana" means "back" and this stage means that the dog goes back to a non-estrus state. This is a quiet time during which her reproductive organs are in a state of rest, even though her pituitary gland is actually preparing for the next proestrus stage. This is the longest stage of the heat cycle lasing from 100 to 150 days.
The Bottom Line
So how long is a female dog's heat cycle? It depends on you really mean for being in "heat." To be technical, the "real heat" stage is the estrus stage which is when you want to introduce your female dog to a male if you are planning on having a batch of puppies. However, if don't want any puppies, it's wise to practice caution and keep your female dog away from male dogs from proestrus up until the end of the estrus stage which is about 3 weeks.